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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="timespec_get.html" title="c/chrono/timespec get"><span class="t-lines"><span>timespec_get</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div></div></td></tr>
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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><strong class="selflink"><span class="t-lines"><span>asctime</span><span>asctime_s</span></span></strong></div><div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="ctime.html" title="c/chrono/ctime"><span class="t-lines"><span>ctime</span><span>ctime_s</span></span></a></div><div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div></div></td></tr>
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<td> <div>定义于头文件 <code>&lt;time.h&gt;</code>
 </div></td>
<td></td>
<td></td>
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<tr class="t-dcl">
<td> <div><span class="mw-geshi c source-c"><span class="kw4">char</span><span class="sy2">*</span>   asctime  <span class="br0">(</span> <span class="kw4">const</span> <span class="kw1">struct</span> <a href="tm.html"><span class="kw522">tm</span></a><span class="sy2">*</span> time_ptr <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (1) </td>
<td class="t-dcl-nopad">  </td>
</tr>
<tr class="t-dcl">
<td> <div><span class="mw-geshi c source-c"><span class="kw4">char</span><span class="sy2">*</span>   asctime_r<span class="br0">(</span> <span class="kw4">const</span> <span class="kw1">struct</span> <a href="tm.html"><span class="kw522">tm</span></a><span class="sy2">*</span> time_ptr, <span class="kw4">char</span><span class="sy2">*</span> buf <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (2) </td>
<td> <span class="t-mark-rev t-since-c2x">(C2x 起)</span> </td>
</tr>
<tr class="t-dcl t-since-c11">
<td> <div><span class="mw-geshi c source-c">errno_t asctime_s<span class="br0">(</span> <span class="kw4">char</span><span class="sy2">*</span> buf, rsize_t bufsz, <span class="kw4">const</span> <span class="kw1">struct</span> <a href="tm.html"><span class="kw522">tm</span></a><span class="sy2">*</span> time_ptr <span class="br0">)</span><span class="sy4">;</span></span></div></td>
<td> (3) </td>
<td> <span class="t-mark-rev t-since-c11">(C11 起)</span> </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
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<div class="t-li1"><span class="t-li">1)</span> 转换日历时间 <span class="t-lc"><a href="tm.html" title="c/chrono/tm">tm</a></span> 为以下固定的 25 字符表示形式： <span class="t-c"><span class="mw-geshi c source-c">Www Mmm dd hh<span class="sy4">:</span>mm<span class="sy4">:</span>ss yyyy\n</span></span>
<ul><li><code>Www</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">time_ptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_wday</span></span> 的星期之日的三字母英文缩写， <code>Mon</code> 、 <code>Tue</code> 、 <code>Wed</code> 、 <code>Thu</code> 、 <code>Fri</code> 、 <code>Sat</code> 、 <code>Sun</code> 之一。
</li><li><code>Mmm</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">time_ptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_mon</span></span> 的月名的三字母英文缩写， <code>Jan</code> 、 <code>Feb</code> 、 <code>Mar</code> 、 <code>Apr</code> 、 <code>May</code> 、 <code>Jun</code> 、 <code>Jul</code> 、 <code>Aug</code> 、 <code>Sep</code> 、 <code>Oct</code> 、 <code>Nov</code> 、 <code>Dec</code> 之一。
</li><li><code>dd</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">timeptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_mday</span></span> 的 2 位月之日，如同由 <span class="t-lc"><a href="../io/fprintf.html" title="c/io/fprintf">sprintf</a></span> 以 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">%</span>2d</span></span> 打印
</li><li><code>hh</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">timeptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_hour</span></span> 的 2 位时，如同由 <span class="t-lc"><a href="../io/fprintf.html" title="c/io/fprintf">sprintf</a></span> 以 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">%</span>.2d</span></span> 打印
</li><li><code>mm</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">timeptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_min</span></span> 的 2 位分，如同由 <span class="t-lc"><a href="../io/fprintf.html" title="c/io/fprintf">sprintf</a></span> 以 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">%</span>.2d</span></span> 打印
</li><li><code>ss</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">timeptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_sec</span></span> 的 2 位秒，如同由 <span class="t-lc"><a href="../io/fprintf.html" title="c/io/fprintf">sprintf</a></span> 以 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">%</span>.2d</span></span> 打印
</li><li><code>yyyy</code> ——来自 <span class="t-c"><span class="mw-geshi c source-c">timeptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_year <span class="sy2">+</span> <span class="nu0">1900</span></span></span> 的 4 位年，如同由 <span class="t-lc"><a href="../io/fprintf.html" title="c/io/fprintf">sprintf</a></span> 以 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">%</span>4d</span></span> 打印</li></ul></div>

<div class="t-li1"><span class="t-li"></span> 若 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>time_ptr</span></span> 的任何成员在其正常范围外则行为未定义</div>
<div class="t-li1"><span class="t-li"></span> 若 <span class="t-c"><span class="mw-geshi c source-c">time_ptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_year</span></span> 所指示的历年拥有多于 4 位数或小于 1000 年则行为未定义。</div>
<div class="t-li1"><span class="t-li"></span> 函数不支持本地化，且不能移除换行符。</div>
<div class="t-li1"><span class="t-li"></span> 函数修改静态存储且非线程安全。</div>
<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，除了写入消息到用户提供的存储 <code>buf</code> 中，保证它是空终止的。</div>
<div class="t-li1"><span class="t-li"></span> 若存储始于 <code>buf</code> 的可用大小小于 26 字节则行为未定义。</div>
<div class="t-li1"><span class="t-li">3)</span> 同 <span class="t-v">(1)</span> ，除了写入消息到用户提供的存储 <code>buf</code> 中，保证它是空终止的。且在运行是检测下列错误并调用当前安装的<a href="../error/set_constraint_handler_s.html" title="c/error/set constraint handler s">制约处理</a>函数：
<dl><dd><ul><li> <code>buf</code> 或 <code>time_ptr</code> 为空指针
</li><li> <code>bufsz</code> 小于 26 或大于 <span class="t-lc">RSIZE_MAX</span>
</li><li> 不是所有 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>time_ptr</span></span> 的成员都在其正常范围内
</li><li> <span class="t-c"><span class="mw-geshi c source-c">time_ptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_year</span></span> 所指示的年小于 0 或大于 9999
</li></ul>
</dd><dd>同所有边界检查函数， <code>asctime_s</code>  仅若实现定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_LIB_EXT1__</span></span> 且用户在包含 <code>time.h</code> 前定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_WANT_LIB_EXT1__</span></span> 为整数常量 1 才保证可用。</dd></dl></div>

<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
<table class="t-par-begin">


<tr class="t-par">
<td>  time_ptr
</td>
<td> -
</td>
<td>  指向指定待打印时间的 <span class="t-lc"><a href="tm.html" title="c/chrono/tm">tm</a></span> 对象的指针
</td></tr>
<tr class="t-par">
<td>  buf
</td>
<td> -
</td>
<td>  指向用户提供的至少有 26 字节的缓冲区的指针
</td></tr>
<tr class="t-par">
<td>  bufsz
</td>
<td> -
</td>
<td>  用户提供的缓冲区大小
</td></tr></table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
<div class="t-li1"><span class="t-li">1)</span> 指向保有如上描述的日期与时间的静态空终止字符串指针。该字符串可能在 <code>asctime</code> 与 <span class="t-lc"><a href="ctime.html" title="c/chrono/ctime">ctime</a></span> 间共享，且可能在每次调用这些函数时被重写。</div>
<div class="t-li1"><span class="t-li">2)</span> <code>buf</code> ，在返回后指向保有如上描述的日期与时间的静态空终止字符串。</div>
<div class="t-li1"><span class="t-li">3)</span> 成功时为零，失败时为非零，并设置 <span class="t-c"><span class="mw-geshi c source-c">buf<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span></span></span> 为零（除非 <code>buf</code> 为空指针或 <code>bufsz</code> 为零或大于 <span class="t-lc">RSIZE_MAX</span> ）。</div>
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
<p><code>asctime</code> 返回指向静态数据的指针从而不是线程安全的。 POSIX 标记此函数为过时并推荐用 <span class="t-lc"><a href="strftime.html" title="c/chrono/strftime">strftime</a></span> 代替。 C 标准亦推荐用 <span class="t-lc"><a href="strftime.html" title="c/chrono/strftime">strftime</a></span> 代替 <code>asctime</code> 、 <code>asctime_r</code> 及 <code>asctime_s</code> 因为 <code>strftime</code> 更灵活且为本地环境相关。
</p><p>POSIX 限制未定义行为仅为当输出字符串将会长于 25 个字符、当 <code>timeptr-&gt;tm_wday</code> 或 <code>timeptr-&gt;tm_mon</code> 不在期待范围内，或当 <code>timeptr-&gt;tm_year</code> 超出 <span class="t-c"><span class="mw-geshi c source-c">INT_MAX<span class="sy2">-</span><span class="nu0">1990</span></span></span> 。
</p><p>一些实现处置 <span class="t-c"><span class="mw-geshi c source-c">timeptr<span class="sy2">-</span><span class="sy1">&gt;</span>tm_mday<span class="sy1">==</span><span class="nu0">0</span></span></span> 为表示前一月的最后一日。
</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">运行此代码</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="c source-c"><pre class="de1"><span class="co2">#define __STDC_WANT_LIB_EXT1__ 1</span>
<span class="co2">#include &lt;time.h&gt;</span>
<span class="co2">#include &lt;stdio.h&gt;</span>
 
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw1">struct</span> <a href="tm.html"><span class="kw522">tm</span></a> <a href="tm.html"><span class="kw522">tm</span></a> <span class="sy1">=</span> <span class="sy2">*</span><a href="localtime.html"><span class="kw519">localtime</span></a><span class="br0">(</span><span class="sy3">&amp;</span><span class="br0">(</span><a href="time_t.html"><span class="kw523">time_t</span></a><span class="br0">)</span><span class="br0">{</span><a href="time.html"><span class="kw513">time</span></a><span class="br0">(</span><a href="../types/NULL.html"><span class="kw103">NULL</span></a><span class="br0">)</span><span class="br0">}</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../io/fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%s"</span>, asctime<span class="br0">(</span><span class="sy3">&amp;</span><a href="tm.html"><span class="kw522">tm</span></a><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
 
<span class="co2">#ifdef __STDC_LIB_EXT1__</span>
    <span class="kw4">char</span> str<span class="br0">[</span><span class="nu0">26</span><span class="br0">]</span><span class="sy4">;</span>
    asctime_s<span class="br0">(</span>str, <span class="kw4">sizeof</span> str, <span class="sy3">&amp;</span><a href="tm.html"><span class="kw522">tm</span></a><span class="br0">)</span><span class="sy4">;</span>
    <a href="../io/fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%s"</span>, str<span class="br0">)</span><span class="sy4">;</span>
<span class="co2">#endif</span>
<span class="br0">}</span></pre></div></div>
<p>可能的输出：
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="text source-text"><pre class="de1">Tue May 26 21:51:50 2015
Tue May 26 21:51:50 2015</pre></div></div> 
</div>
<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
<div class="t-ref-std-11">
<ul><li> C11 standard (ISO/IEC 9899:2011): 
</li></ul>
<dl><dd><ul><li> 7.27.2.1 The asctime function (p: 392-393)
</li></ul>
</dd></dl>
<dl><dd><ul><li> K.3.8.2.1 The asctime_s function (p: 624-625)
</li></ul>
</dd></dl>
<div class="t-ref-std-c99">
<ul><li> C99 standard (ISO/IEC 9899:1999): 
</li></ul>
<dl><dd><ul><li> 7.23.3.1 The asctime function (p: 341-342)
</li></ul>
</dd></dl>
<div class="t-ref-std-c89">
<ul><li> C89/C90 standard (ISO/IEC 9899:1990): 
</li></ul>
<dl><dd><ul><li> 4.12.3.1 The asctime function 
</li></ul>
</dd></dl>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="ctime.html" title="c/chrono/ctime"> <span class="t-lines"><span>ctime</span><span>ctime_s</span></span></a></div><div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div></div>
</td>
<td>   将 <code>struct time_t</code> 对象转换成文本表示 <br> <span class="t-mark">(函数)</span> </td></tr>

<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="strftime.html" title="c/chrono/strftime"> <span class="t-lines"><span>strftime</span></span></a></div></div>
</td>
<td>  将 <code>struct tm</code> 对象转换成自定义文本表示 <br> <span class="t-mark">(函数)</span> </td></tr>

</table></div>
</div>

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